Calibration of an ecological model of a eutrophic coastal lagoon and assessment of the effect of management strategies on dissolved oxygen.

Eutrophication is one of the biggest ecological concerns for water bodies worldwide. Shallow coastal areas under high anthropogenic pressure are particularly vulnerable to water quality deterioration. This work presents the development of a two-dimensional ecological model of the processes in the Orbetello Lagoon (central Italy), a highly eutrophic coastal basin subject to several human-induced and natural stressors. The ecological model, coupled with a hydrodynamic model, simulates the nutrient cycle in the water column and in the sediment, the growth and decay of rooted vegetation, macroalgae, phytoplankton, and zooplankton, as well as the oxygen cycle. Once calibrated and validated with field measurements, the model has been used as a decision-support tool for lagoon management, providing qualitative insights into the impact of various stress factors and intervention actions. This study allowed the quantification of the effects on dissolved oxygen of different interventions (pumping systems, removal of obstructions at inlets, channels dredging), proving that the minimum dissolved oxygen concentration in the lagoon in the summer months is relevantly affected by the human intervention on the system.